The long-term objective of this research is to understand how chromatin remodeling controls the development of the vertebrate eye and to dissect the molecular basis of congenital cataract formation. As in all developmental pathways, eye development depends upon precise regulation of spatial and temporal patterns of gene expression. Transcription activation and repression occurs in the context of chromatin, a complex of DNA and histone proteins that compacts DNA into the eukaryotic nucleus. Chromatin remodeling enzymes and histone modifying enzymes cooperatively regulate the accessibility of DNA in chromatin, and are thereby essential regulators of gene expression. We are specifically interested in how the Imitation Switch (ISWl) chromatin remodeling enzyme controls eye development in the early embryo, and how the loss of ISWl function leads to cataracts in the frog Xenopus laevis. To accomplish this, we will, prevent ISWl function in developing Xenopus embryos, and specifically within the developing eye, and analyze the resulting eye malformations by a number of methods, including microscopic examination, sectioning and fine structure analysis, and gene expression analysis. These studies will provide critical insights into the role of chromatin remodeling in eye development and will provide a new experimental system in which to study cataract formation. This proposal has three specific aims. Aim 1 is to characterize the developmental defects in the eyes of Xenopus embryos lacking normal levels of ISWl protein, addressing both morphological and transcriptional defects in the developing eye. Aim 2 is to identify which ISWI-containing complex is responsible for normal eye development, using Morpholino inhibition of subunits unique to each of the known Xenopus ISWI complexes. Aim 3 is to test whether ISWl function is required specifically in the developing eye for normal development and to prevent cataracts, by generating transgenic Xenopus that express a dominant-negative ISWI mutant under control of the gamma-crystallin promoter.